Hitches are in wide use for towing many kinds of trailer vehicles by towing vehicles. Most traditional hitches comprise the combination of a first coupling means (for example, a ball) attached to one of the vehicles and a second coupling means (for example, a hollow, hemispherical coupler) attached to the other. Since such conventional coupling means are fixedly attached to the vehicles, it is necessary for the vehicles to be brought into precise alignment in order to achieve coupling. This can be a difficult and time-consuming task. In circumstances where precise alignment is not achieved, it may be possible to manually move the trailer vehicle to a position for coupling to the towing vehicle. While this may be acceptable for lightweight trailer vehicles, it is a near-impossible task for heavier trailer vehicles such as loaded airport freight carts. Persons attempting to manually position a heavy trailer vehicle may suffer injuries.
Further, it is desirable to prevent the need for a second person to assist in coupling the towing and trailer vehicles. In general, having a second person, located behind the towing vehicle, to direct the operator of the towing vehicle presents dangerous circumstances. Further, it is inefficient to require two people to achieve a result which could be accomplished by a single person.
In general, the prior art has attempted to address these problems with the provision of a hitch assembly comprising a tongue or rod which is slidably insertable into a housing mounted on one of the vehicles and which is capable of some longitudinal and lateral movement so that a rearward end of the tongue, fitted with a coupling means, can be manually positioned to engage the corresponding coupling means on the other vehicle. The hitch assemblies of some prior art references provide an automatic locking mechanism which locks the tongue into a "locked" position.
However, the prior art hitch assemblies may suffer from one or more disadvantages. For example, several prior art hitch assemblies have been designed in such a way that it is only possible for the tongue to move to the "locked" position after the tongue becomes aligned with the vehicles. As a result, after the vehicles are coupled and the towing vehicle is moved forward from a slightly displaced lateral position (relative to the trailer vehicle), the tongue may be susceptible to banging from side to side within the housing until the tongue and the two vehicles achieve precise alignment. This is disadvantageous since it: (1) may damage the sides of the housing, ultimately requiring repair or replacement; and (2) may place undue pressure on the pivot pin retaining the proximal end of the tongue within the housing. After a period of time, the pin may become damaged to the point where repair or replacement is necessary.
Along the same lines, several prior art hitch assemblies are designed in such a way that lateral movement of the tongue is not immediately possible after the locking mechanism is disengaged. Rather, the operator is required to withdraw the tongue entirely, or nearly so, from within the housing until lateral movement of the tongue is possible. This limits the use of the hitch assembly. In some circumstances, the operator may have backed the towing vehicle into close proximity to the trailer vehicle so that the tongue cannot be fully withdrawn since it will engage the front portion of the trailer vehicle. Since lateral movement is then not possible (since the tongue is not capable of being fully extended from the housing), the operator would be forced to get back into the towing vehicle and move it ahead to create sufficient space between the vehicles to enable full extension of the tongue, and thus, lateral movement of the tongue. This adds unnecessary time and effort into the process, and could be eliminated if one could laterally position the tongue immediately upon disengagement of the locking mechanism.
Prior art hitch assemblies which may suffer from one or both of the above-noted disadvantages are described in: U.S. Pat. No. 3,912,119, issued to Hill et al., U.S. Pat. No. 2,871,029, issued to Demarest, U.S. Pat. No. 3,860,267, issued to Lyons and U.S. Pat. No. 4,991,865, issued to Francisco.
The hitch assemblies described in Demarest, Hill et al., and Francisco may be susceptible to damage to the housing while the tongue is moving into the housing and towards its locked position from either side-to-side banging of the tongue therein, or from the longitudinal engagement of a proximal end of the tongue on a closed interior of the housing.
Other prior art hitch assemblies include overly complex mechanisms which may render the hitch assembly too expensive for commercial application or too cumbersome for retrofitting existing towing vehicles. For example, U.S. Pat. No. 4,558,883, issued to Bouma, discloses such a complicated hitch mechanism.
Some prior art hitch assemblies, such as the one disclosed in U.S. Pat. No. 5,277,447, issued to Blaser, disclose housing and tongue designs which allow limited lateral movement of the tongue. This may be disadvantageous if the towing vehicle is sufficiently misaligned relative to the trailer vehicle to be outside the lateral movement range of the tongue. Repeated positioning of the towing vehicle relative to the trailer vehicle would be required to overcome such a limitation.